Pest control. Protecting endangered species often involves devising humane and effective pest control methods. There are several species of animals that were introduced into New Zealand long ago that directly attack or damage the habitat of our native animals, especially our flightless ground-dwelling birds. These include cats, dogs, ferrets, possums, rats, stoats and weasels. Animal-based scientists contribute to controlling their numbers, for example, by working out which traps or poisons cause the least suffering to possums, how to avoid killing non-target animals and how, in a pain-free way, to prevent the birth and rearing of baby possums.